The present invention relates to a new and improved construction of a gear wheel machine, especially a gear pump for pumping polymer solutions or melts.
In its more specific aspects the invention relates to a new and improved construction of gear pump comprising a housing containing a gear space or chamber formed therein, at least two shafts extending in parallelism and through the gear chamber or space, and a gear wheel or gear is provided on each one of the shafts. End or closure bushes are inserted into the housing and laterally bound the gear chamber or space and form axial bearings for the gear wheels or gears by means of their inner end faces. There are also provided bearing bushes, each of which is inserted into a respective one of the end bushes and form a radial bearing for a respective one of the shafts, and cover members are laterally mounted on the housing and support the end bushes including the bearing bushes against an outwardly directed axial displacement.
In a gear pump of this type as known, for example, from German Patent Publication No. 2,432,180, published May 20, 1976, the outer or exterior end surfaces or faces of the end or closure bushes and the bearing bushes directly engage the cover members which are secured to the pump housing by outer screws or threaded bolts and which are screwed directly to the end bushes by inner screws or threaded bolts. When the bearing bushes are worn and have to be exchanged, the shafts including the associated gears or gear wheels, bearing bushes and end bushes can be axially pushed out of the housing after the cover members have been released. In case that the bearing bushes have become seized upon the shafts, then it may be extremely difficult to remove the same from the shafts without damaging either the shafts or the gear wheels. Above all, this is true in the event the shafts and the associated gears or gear wheels are formed in one piece. In such case the gear wheels cannot be displaced upon the shafts even after these have been removed from the housing, and thus, the gear wheels cannot be utilized to push the bearing bushes off the shaft.